1. Field of the Invention
The present invention relates to method and apparatus for the improved uniform distribution of a liquid over a filter surface, and, more especially, relates to the uniform distribution of a slurry or wash liquid over a flat, horizontal filtering surface, e.g., a continuous vacuum filter. By "wash liquid" as utilized herein, there is intended any liquid which may upon use become saturated, loaded or greatly contaminated with solids.
2. Description of the Prior Art
In the known filters of the subject type, irregularity in flow or distribution may reduce the filtering capacity and the yield of the wash process. The regularity of the flow of the product to be filtered or of the wash liquid is typically assured by means of feed-distribution boxes.
Specifically, there are known feed-distribution boxes which, when mounted above a moving, e.g., rotating, filter surface, have a width essentially equal to that of the filter medium surface and wherein the product to be filtered is serially introduced into two successive compartments, passing from one compartment to the other via an overflow partition. Feed-distribution boxes of this type are especially adapted for the horizontal filter described in U.S. Pat. No. 3,262,574 which is suited for filtration of phosphoric acid slurries having a high solids content in gypsum. This device affords a good distribution of solids and a minimum risk of decantation of the slurries to be filtered. It also exhibits the advantage of depositing the slurry onto the filter in the downward direction and not by means of an overflow system, which would be dependent on the box being precisely horizontal.
There too is known the apparatus described in published French Patent Application No. 2,322,640 [Belgian Pat. No. 845,843], wherein the homogeneity of a slurry to be filtered is attained by means of a vertically adjustable partition between the two compartments; further, the apparatus of U.S. Pat. No. 3,626,486 is also known, same illustrating the known system of overflow and insures the uniformity of flow onto a circular filter by means of a gate having a variable opening. Cf. U.S. Pat. No. 3,426,908; Proceedings of the 16th Annual Meeting, Fertilizer Industry Round Table, pp. 52-60 (1966).
Nonetheless, a need still exists in this art for further insuring absence of decantation in such systems, and concomitant avoidance of any clogging of the filter media.